Adding virtualenvs to gitignore
Adding travis build for py27, py34

Installing pyside and pyqt4 using pip

fixes #5
Installing pyqt only in Python 2.7

Since pyqt is not available on PyPI, we can't install
it using pip, relying only on apt-get to install it
if we are in python 2.7.

PySide is available, but in order to reduce build time
we also install it using apt-get when in Python 2.7.
Updated docs about requirements